Honeycomb filter

Abstract

A honeycomb filter, including: a honeycomb structure, wherein the honeycomb structure further includes a platinum group element-containing catalyst layer and a trapping layer, the platinum group element-containing catalyst layer is disposed at least on an entire surface of a side of an inner surface of the partition walls surrounding either one of the inflow cells or the outflow cells, the trapping layer does not contain a platinum group element, and the trapping layer is disposed in a range of at least up to 50% with respect to an overall length of the honeycomb structure starting from the outflow end face and is not disposed in a range of at least up to 40% with respect to the overall length starting from the inflow end face, in an extending direction of the cells of the honeycomb structure.

What is claimed is: 
     
       1. A honeycomb filter, comprising:
 a honeycomb structure which has porous partition walls disposed so as to surround a plurality of cells as through channels of fluid extending from an inflow end face to an outflow end face; and 
 plugging portions disposed to plug either one of end portions of each of the cells on the side of the inflow end face or the side of the outflow end face, 
 wherein the cells in which the plugging portions are arranged in the end portion on the side of the outflow end face and which are opened on the side of the inflow end face are defined as inflow cells, 
 the cells in which the plugging portions are arranged in the end portion on the side of the inflow end face and which are opened on the side of the outflow end face are defined as outflow cells, 
 the honeycomb structure further includes a platinum group element-containing catalyst layer constituted by an exhaust gas purifying catalyst containing a platinum group element and a trapping layer which traps particulate matter in exhaust gas, 
 the platinum group element-containing catalyst layer is disposed at least on an entire surface of a side of an inner surface of the partition walls surrounding either one of the inflow cells or the outflow cells, 
 the platinum group element-containing catalyst layer is present only on a side of a surface of the partition walls in a thickness direction of the partition walls, 
 the trapping layer does not contain a platinum group element, 
 the trapping layer is disposed on a side of a second surface positioned on an opposite side of a first surface of the partition walls having the platinum group element-containing catalyst layer disposed on the entire surface thereof, and 
 the trapping layer is disposed in a range of at least up to 50% with respect to an overall length of the honeycomb structure starting from the outflow end face and is not disposed in a range of at least up to 40% with respect to the overall length starting from the inflow end face, in an extending direction of the cells of the honeycomb structure. 
 
     
     
       2. The honeycomb filter according to  claim 1 , wherein a porosity of the platinum group element-containing catalyst layer is from 50% to 90%. 
     
     
       3. The honeycomb filter according to  claim 1 , wherein a thickness of the platinum group element-containing catalyst layer is from 10 μm to 40 μm. 
     
     
       4. The honeycomb filter according to  claim 1 , wherein the platinum group element-containing catalyst layer is a catalyst layer containing an oxide of at least one element selected from the group consisting of aluminum, zirconium, and cerium. 
     
     
       5. The honeycomb filter according to  claim 1 , wherein a porosity of the trapping layer is from 70% to 90%. 
     
     
       6. The honeycomb filter according to  claim 1 , wherein a thickness of the trapping layer is from 10 μm to 50 μm. 
     
     
       7. The honeycomb filter according to  claim 1 , wherein the trapping layer is a layer containing an oxide of at least one element selected from the group consisting of aluminum, magnesium, zirconium, cerium, and silicon. 
     
     
       8. The honeycomb filter according to  claim 1 , wherein the platinum group element-containing catalyst layer is disposed on at least a part of the side of the second surface of the partition walls in a range of up to 60% with respect to the overall length starting from the inflow end face in the extending direction of the cells of the honeycomb structure.